scholarly journals Cell competition is driven by Xrp1-mediated phosphorylation of eukaryotic initiation factor 2α

PLoS Genetics ◽  
2021 ◽  
Vol 17 (12) ◽  
pp. e1009958
Author(s):  
Naotaka Ochi ◽  
Mai Nakamura ◽  
Rina Nagata ◽  
Naoki Wakasa ◽  
Ryosuke Nakano ◽  
...  
Keyword(s):  
Er Stress ◽  
Cell Interaction ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Bzip Transcription Factor ◽  
Cell Competition ◽  
Eukaryotic Translation ◽  
Global Protein Synthesis ◽  
Eukaryotic Translation Initiation ◽  
Dependent Cell

Cell competition is a context-dependent cell elimination via cell-cell interaction whereby unfit cells (‘losers’) are eliminated from the tissue when confronted with fitter cells (‘winners’). Despite extensive studies, the mechanism that drives loser’s death and its physiological triggers remained elusive. Here, through a genetic screen in Drosophila, we find that endoplasmic reticulum (ER) stress causes cell competition. Mechanistically, ER stress upregulates the bZIP transcription factor Xrp1, which promotes phosphorylation of the eukaryotic translation initiation factor eIF2α via the kinase PERK, leading to cell elimination. Surprisingly, our genetic data show that different cell competition triggers such as ribosomal protein mutations or RNA helicase Hel25E mutations converge on upregulation of Xrp1, which leads to phosphorylation of eIF2α and thus causes reduction in global protein synthesis and apoptosis when confronted with wild-type cells. These findings not only uncover a core pathway of cell competition but also open the way to understanding the physiological triggers of cell competition.

scholarly journals APOL1 risk variants cause podocytes injury through enhancing endoplasmic reticulum stress

2018 ◽  
Vol 38 (4) ◽  
Author(s):  
Hongxiu Wen ◽  
Vinod Kumar ◽  
Xiqian Lan ◽  
Seyedeh Shadafarin Marashi Shoshtari ◽  
Judith M. Eng ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Er Stress ◽  
Kidney Diseases ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Wild Type ◽  
Eukaryotic Translation ◽  
Risk Variants ◽  
Eukaryotic Translation Initiation ◽  
Underlying Mechanisms

Two coding sequence variants (G1 and G2) of Apolipoprotein L1 (APOL1) gene have been implicated as a higher risk factor for chronic kidney diseases (CKD) in African Americans when compared with European Americans. Previous studies have suggested that the APOL1 G1 and G2 variant proteins are more toxic to kidney cells than the wild-type APOL1 G0, but the underlying mechanisms are poorly understood. To determine whether endoplasmic reticulum (ER) stress contributes to podocyte toxicity, we generated human podocytes (HPs) that stably overexpressed APOL1 G0, G1, or G2 (Vec/HPs, G0/HPs, G1/HPs, and G2/HPs). Propidium iodide staining showed that HP overexpressing the APOL1 G1 or G2 variant exhibited a higher rate of necrosis when compared with those overexpressing the wild-type G0 counterpart. Consistently, the expression levels of nephrin and podocin proteins were significantly decreased in the G1- or G2-overexpressing cells despite the maintenance of their mRNA expressions levels. In contrast, the expression of the 78-kDa glucose-regulated protein ((GRP78), also known as the binding Ig protein, BiP) and the phosphorylation of the eukaryotic translation initiation factor 1 (eIF1) were significantly elevated in the G1/HPs and G2/HPs, suggesting a possible occurrence of ER stress in these cells. Furthermore, ER stress inhibitors not only restored nephrin protein expression, but also provided protection against necrosis in G1/HPs and G2/HPs, suggesting that APOL1 risk variants cause podocyte injury partly through enhancing ER stress.

scholarly journals The eukaryotic translation initiation factor eIF4E elevates steady-state m7G capping of coding and noncoding transcripts

2020 ◽  
Vol 117 (43) ◽  
pp. 26773-26783 ◽  
Author(s):  
Biljana Culjkovic-Kraljacic ◽  
Lucy Skrabanek ◽  
Maria V. Revuelta ◽  
Jadwiga Gasiorek ◽  
Victoria H. Cowling ◽  
...  
Keyword(s):  
Steady State ◽  
Translation Initiation ◽  
Noncoding Rnas ◽  
Cell Interaction ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Protein Coding ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation

Methyl-7-guanosine (m7G) “capping” of coding and some noncoding RNAs is critical for their maturation and subsequent activity. Here, we discovered that eukaryotic translation initiation factor 4E (eIF4E), itself a cap-binding protein, drives the expression of the capping machinery and increased capping efficiency of ∼100 coding and noncoding RNAs. To quantify this, we developed enzymatic (cap quantification; CapQ) and quantitative cap immunoprecipitation (CapIP) methods. The CapQ method has the further advantage that it captures information about capping status independent of the type of 5′ cap, i.e., it is not restricted to informing on m7G caps. These methodological advances led to unanticipated revelations: 1) Many RNA populations are inefficiently capped at steady state (∼30 to 50%), and eIF4E overexpression increased this to ∼60 to 100%, depending on the RNA; 2) eIF4E physically associates with noncoding RNAs in the nucleus; and 3) approximately half of eIF4E-capping targets identified are noncoding RNAs. eIF4E’s association with noncoding RNAs strongly positions it to act beyond translation. Coding and noncoding capping targets have activities that influence survival, cell morphology, and cell-to-cell interaction. Given that RNA export and translation machineries typically utilize capped RNA substrates, capping regulation provides means to titrate the protein-coding capacity of the transcriptome and, for noncoding RNAs, to regulate their activities. We also discovered a cap sensitivity element (CapSE) which conferred eIF4E-dependent capping sensitivity. Finally, we observed elevated capping for specific RNAs in high-eIF4E leukemia specimens, supporting a role for cap dysregulation in malignancy. In all, levels of capping RNAs can be regulated by eIF4E.

scholarly journals Regulation of eIF6 through multisite and sequential phosphorylation by GSK3β

2018 ◽  
Author(s):  
Courtney F. Jungers ◽  
Jonah M. Elliff ◽  
Daniela S. Masson-Meyers ◽  
Christopher J. Phiel ◽  
Sofia Origanti
Keyword(s):  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Serum Starvation ◽  
Ribosomal Subunits ◽  
Eukaryotic Translation ◽  
Induced Stress ◽  
C Terminus ◽  
Global Protein Synthesis ◽  
Eukaryotic Translation Initiation ◽  
Response To Stress

AbstractEukaryotic translation initiation factor 6 is essential for the synthesis of 60S ribosomal subunits and for regulating the association of 60S and 40S subunits. A mechanistic understanding of how eIF6 modulates translation in response to stress, specifically starvation-induced stress, is lacking. Our studies have uncovered a novel mode of eIF6 regulation by GSK3 that is predominantly active in response to serum starvation. Human eIF6 is phosphorylated by GSK3β at a multisite motif in the C-terminus. Sequential phosphorylation by GSK3β requires phosphorylation at a priming site. In response to serum starvation, eIF6 accumulates in the cytoplasm and this altered localization is dependent on GSK3. Disruption of eIF6 phosphorylation enhances translation inhibition and markedly sensitizes the cells to serum starvation. These results suggest that eIF6 regulation by GSK3β contributes to the attenuation of global protein synthesis that is critical for adaptation to starvation-induced stress.

scholarly journals Molecular docking studies of salubrinal and its analogs as inhibitors of the GADD34:PP1 enzyme

ADMET & DMPK ◽  
2019 ◽  
Vol 7 (2) ◽  
pp. 140-150 ◽  
Author(s):  
Pavlo V. Zadorozhnii ◽  
Ihor O. Pokotylo ◽  
Vadym V. Kiselev ◽  
Oxana V. Okhtina ◽  
Aleksandr V. Kharchenko
Keyword(s):  
Molecular Docking ◽  
Er Stress ◽  
Binding Site ◽  
Translation Initiation ◽  
Protein Molecule ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Eukaryotic Translation ◽  
Eukaryotic Translation Initiation

The phenomenon of the endoplasmic reticulum (ER) stress as a molecular pathophysiological process underlies diseases as cancer, diabetes mellitus, myocardial infarction, neurodegenerative disorders, diseases of the urinary system, disorders associated with bone integrity, etc. To prevent ER stress, salubrinal, which is a phosphatase inhibitor of the eukaryotic translation initiation factor - GADD34:PP1, is currently being intensively studied. The aim of this work is to search for new analogues of this drug using molecular docking methods. Optimization of the geometry of the studied structures and molecular docking was carried out using the ArgusLab 4.0.1 software package. The three-dimensional crystal structure of the GADD34: PP1 enzyme (PDB ID: 4XPN) was loaded in the PDB format from the protein molecule data bank. The model of the binding site was created on the basis of the phosphoric acid residue (403 PO4). The dimensions of the binding site were set manually and were 40.000 Å along the X-axis, 40.000 Å - the Y-axis and 40.000 Å - the Z-axis. The docking was done with a flexible ligand, and the semi-empirical AScore function was used for the scoring procedure. It was shown that for the salubrinal molecule the most favorable was the conformation stabilized by the intramolecular hydrogen bond formed between the hydrogen atom of the thiourea fragment and the oxygen atom of the amide fragment. According to molecular docking data, six compounds from the fifty-four analyzed analogues of salubrinal exceed it in the stability of the complex formed with GADD34:PP1. The results of this work can be used to create new phosphatase inhibitors of the eukaryotic translation initiation factor GADD34:PP1.

scholarly journals GNRH Induces the Unfolded Protein Response in the LβT2 Pituitary Gonadotrope Cell Line

2009 ◽  
Vol 23 (1) ◽  
pp. 100-112 ◽  
Author(s):  
Minh-Ha T. Do ◽  
Sharon J. Santos ◽  
Mark A. Lawson
Keyword(s):  
Er Stress ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation ◽  
Unfolded Protein ◽  
Eukaryotic Translation Initiation ◽  
The Unfolded Protein Response ◽  
Protein Response ◽  
Upr Pathway

The neuropeptide GNRH 1 stimulates the secretion of the reproductive hormone LH in pituitary gonadotropes. Other secretory cell types depend on the unfolded protein response (UPR) pathway to regulate protein synthesis and protect against endoplasmic reticulum (ER) stress in response to differentiation or secretory stimuli. This study investigated the role of the UPR in GNRH action within the LβT2 gonadotrope model. Cells were treated with GNRH, and the activation of UPR signaling components and general translational status was examined. The ER-resident stress sensors, Atf6, Eif2ak3, and Ern1, are all present, and GNRH stimulation results in the phosphorylation of eukaryotic translation initiation factor 2A kinase 3 and its downstream effector, eukaryotic translation initiation factor 2A. Additionally, activation of the UPR was confirmed both in LβT2 as well as mouse primary pituitary cells through identifying GNRH-induced splicing of Xbp1 mRNA, a transcription factor activated by splicing by the ER stress sensor, ER to nucleus signaling 1. Ribosome profiling revealed that GNRH stimulation caused a transient attenuation in translation, a hallmark of the UPR, remodeling ribosomes from actively translating polysomes to translationally inefficient ribonucleoprotein complexes and monosomes. The transient attenuation of specific mRNAs was also observed. Overall, the results show that GNRH activates components of the UPR pathway, and this pathway may play an important physiological role in adapting the ER of gonadotropes to the burden of their secretory demand.

scholarly journals Activation-dependent substrate recruitment by the eukaryotic translation initiation factor 2 kinase PERK

2006 ◽  
Vol 172 (2) ◽  
pp. 201-209 ◽  
Author(s):  
Stefan J. Marciniak ◽  
Lidia Garcia-Bonilla ◽  
Junjie Hu ◽  
Heather P. Harding ◽  
David Ron
Keyword(s):  
Er Stress ◽  
Translation Initiation ◽  
Translation Initiation Factor ◽  
Initiation Factor ◽  
Eukaryotic Translation Initiation Factor ◽  
Α Subunit ◽  
Eukaryotic Translation ◽  
Initiation Factor 2 ◽  
Eukaryotic Translation Initiation ◽  
Translation Initiation Factor 2

Regulated phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α) by the endoplasmic reticulum (ER) stress-activated protein kinase PERK modulates protein synthesis and couples the production of ER client proteins with the organelle's capacity to fold and process them. PERK activation by ER stress is known to involve transautophosphorylation, which decorates its unusually long kinase insert loop with multiple phosphoserine and phosphothreonine residues. We report that PERK activation and phosphorylation selectively enhance its affinity for the nonphosphorylated eIF2 complex. This switch correlates with a marked change to the protease sensitivity pattern, which is indicative of a major conformational change in the PERK kinase domain upon activation. Although it is dispensable for catalytic activity, PERK's kinase insert loop is required for substrate binding and for eIF2α phosphorylation in vivo. Our findings suggest a novel mechanism for eIF2 recruitment by activated PERK and for unidirectional substrate flow in the phosphorylation reaction.

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